Ultrathin cobalt-alloyed barrier layers for copper metallization by a new seeding and electroless-deposition process

Pioneering activation-seeding processes grow catalytic particles with sizes exceeding 10 nm due to agglomeration, and thus are unable to act as a template for electroless deposition of a barrier layer with a thickness of 10 nm or less, which is desperately needed for the incoming ULSI copper interconnecting technology. In this work, the capacity of a seeding process to grow a continuous Co-P barrier layer of 8-nm thickness on thermally oxidized SiO2 layers using electroless deposition will be demonstrated. The Co-P barrier layer works effectively in retarding (a) Cu agglomeration and (b) Cu diffusion into the dielectric layer subjected to thermal annealing. Evidently, thermal stability of the Cu film on SiO2 is markedly strengthened by interposing the 8-nm-thick barrier layer. The mechanism of the interposed barrier layer in enhancing thermal stability of the metallization layer is currently under investigation.